title: Zinc in depression: a meta-analysis.
abstract: BACKGROUND
  Zinc is an essential micronutrient with diverse biological roles in cell growth, apoptosis and metabolism, and in the regulation of endocrine, immune, and neuronal functions implicated in the pathophysiology of depression. This study sought to quantitatively summarize the clinical data comparing peripheral blood zinc concentrations between depressed and nondepressed subjects.
  
  
  METHODS
  PubMed, Cumulated Index to Nursing and Allied Health Literature, and PsycINFO were searched for original peer-reviewed studies (to June 2012) measuring zinc concentrations in serum or plasma from depressed subjects (identified by either screening or clinical criteria) and nondepressed control subjects. Mean (±SD) zinc concentrations were extracted, combined quantitatively in random-effects meta-analysis, and summarized as a weighted mean difference (WMD).
  
  
  RESULTS
  Seventeen studies, measuring peripheral blood zinc concentrations in 1643 depressed and 804 control subjects, were included. Zinc concentrations were approximately -1.85 µmol/L lower in depressed subjects than control subjects (95% confidence interval: [CI]: -2.51 to -1.19 µmol/L, Z17 = 5.45, p < .00001). Heterogeneity was detected (χ(2)17 = 142.81, p < .00001, I(2) = 88%) and explored; in studies that quantified depressive symptoms, greater depression severity was associated with greater relative zinc deficiency (B = -1.503, t9 = -2.82, p = .026). Effect sizes were numerically larger in studies of inpatients (WMD -2.543, 95% CI: -3.522 to -1.564, Z9 = 5.09, p < .0001) versus community samples (WMD -.943, 95% CI: -1.563 to -.323, Z7 = 2.98, p = .003) and in studies of higher methodological quality (WMD -2.354, 95% CI: -2.901 to -1.807, Z7 = 8.43, p < .0001).
  
  
  CONCLUSIONS
  Depression is associated with a lower concentration of zinc in peripheral blood. The pathophysiological relationships between zinc status and depression, and the potential benefits of zinc supplementation in depressed patients, warrant further investigation.
authors.affiliation: Neuropsychopharmacology Research Group, Sunnybrook Research Institute, University of Toronto, Toronto, Ontario, Canada; Toronto Rehabilitation Institute, University of Toronto, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Walter
authors.initials: W
authors.lastname: Swardfager
authors.forename: Nathan
authors.initials: N
authors.lastname: Herrmann
authors.forename: Graham
authors.initials: G
authors.lastname: Mazereeuw
authors.forename: Kyle
authors.initials: K
authors.lastname: Goldberger
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Harimoto
authors.forename: Krista L
authors.initials: KL
authors.lastname: Lanctôt
mesh_terms: D016208:Databases, Factual / Q000706:statistics & numerical data; D003863:Depression / Q000097:blood*; D006801:Humans; D015032:Zinc / Q000097:blood*
chemical_list: D015032:Zinc
keywords: Depression; depressive symptoms; major depressive disorder; micronutrient; trace metal; zinc